This invention generally relates to downhole tools, namely subsurface safety valves.
Safety regulations exist that require the placement of two mechanical pressure containment barriers at all times between the produced fluids in a wellbore and the environment. In subsea completions, when the blow out preventer or tree is removed, it has been general practice to close the surface controlled subsurface safety valve and install a tubing hanger plug by wireline prior to the removal thereby fulfilling the two barrier requirement. However, operators would rather not perform wireline interventions since they are generally costly, time-consuming, and invasive. The prior art would therefore benefit from a pressure barrier mechanism that fulfills the two barrier requirement and does not involve a wireline intervention.
In addition, the reliability and safety of each pressure barrier mechanism used in a subsea completion is highly critical. The accidental or inadvertent opening or closing of any of the pressure barrier mechanisms can result in a dangerous situation to personnel and equipment. Such accidental and inadvertent activations can be the result of leak paths formed in the mechanisms. It would thus also be beneficial to provide a pressure barrier mechanism that remains in its current position (either open or closed) despite the development of a leak path therein.
Also of relevance, lubricators can be used to add or remove sections from a tool string. It would be beneficial to provide a pressure barrier mechanism that could also be used as a downhole lubricator.